Our current research program is concerned with studying the enzymology of polyoma DNA metabolism. At the present time we are concentrating our efforts on three distinct projects. First, we are carrying out studies on an endonuclease activity associated with highly purified polyoma virus particles, attempting to determine if the enzyme protein present in the virus originates from the host or is specified by the viral DNA. Secondly, studies are being carried out on the endonuclease activity present in nuclei of uninfected cells, and cells infected with polyoma virus. Our major emphasis has been to devise procedures which allow the nuclear endonuclease activity to be resolved into multiple components thus providing a means to determine if certain components are observed only after viral infection. Finally we are carrying out studies on the in vitro synthesis of polyoma DNA attempting to establish a system which will initiate DNA synthesis in vitro.